The present disclosure relates to a coolant cap used on an automobile cooling system, in particular, to a threaded coolant cap that prevents excessive torque from being applied to the cap threads as the cap is screwed onto a threaded radiator filler neck. The disclosure may also prevent removal of the cap while the coolant is pressurized, prevent excessive coolant pressure from building up in the system, and prevent a vacuum from occurring in the system relative to the atmospheric pressure when the coolant approaches ambient temperature.
Applying excessive torque while screwing a coolant cap onto a radiator or system filler neck may damage the cap, seals, threads, or make removing the cap difficult. Removing the cap while the coolant is hot and under pressure could cause serious injury. Allowing excessive pressure to build up in the cooling system beyond that for which the cooling system is designed could result in equipment failure and also personal injury. If a pressure relief valve bleeds coolant or vapor from the system when it is heated and expands, subsequent cooling and contraction of the coolant may create a vacuum in the system. Such a vacuum can make removing the cap difficult and could damage components of the cooling system not designed to withstand a net external pressure. The present disclosure addresses these problems.
According to the present disclosure, a coolant cap is adapted to be coupled to a threaded filler neck of a coolant reservoir, the coolant cap including a cover, a main body, and a torque override. The main body includes threads for engagement with the threads of the filler neck. The torque override transmits torque applied to the cover to the main body, enables the threads of main body to engage the threads of the filler neck, and limits the maximum torque that can be transmitted from the cover to the main body.
In the disclosed embodiment, the torque override includes fingers descending from the top wall of the cover, teeth on the main body upper wall, and an override spring, where each of the teeth has a first and a second flank. The first flank engages the fingers when the cap is turned clockwise so as to screw the cap threads onto the filler neck threads while the fingers apply a downward axial force on the main body teeth. The first flank is raked at a high angle so as to be inefficient at transmitting torque to the threads. The override spring is disposed between the cover and main body, so as to engage the cover and main body towards each other so that the teeth and fingers engage except the pressure is present in the system.
The torque transmission permits torque to be transmitted from the cover to the main body to unscrew the main body from the filler neck. When the counterclockwise or unscrewing torque is applied, the second flank of the teeth engage the fingers transmitting the unscrewing torque to the threads. The second flank of the teeth are raked nearly perpendicularat a low angle, so no downward force is required to keep the teeth engaged while unscrewing the cap.
The override spring disposed between the cover and main body pushes the cover and main body towards each other so that the teeth and fingers are normally engaged.
The cap also includes a pressure lock that prevents torque from being transmitted from the cover to the main body that would unscrew the main body from the filler neck while the coolant in the radiator is pressurized. The force of the coolant pressure acts on a valve body which transmits the force to the cap cover, preventing the teeth and fingers of the torque transmission means from being engaged. The coolant pressure is opposed by the override spring to provide a threshhold disengagement pressure greater than zero.
The cap also includes a pressure relief that prevents coolant pressure from exceeding an predetermined upper level. When the coolant pressure is below the predetermined upper level, a pressure relief spring holds a pressure relief piston in a closed position. When the pressure exceeds the predetermined level, the force on the relief piston causes the relief spring to compress and permits fluid to leak past the relief piston.
The cap also includes a vacuum relief that prevents the coolant pressure from falling below a lower predetermined level. When the coolant pressure is above a lower predetermined level, a vacuum relief spring holds the a vacuum relief seal ring closed against a relief piston. When the coolant pressure falls below the lower predetermined level, the force on the relief piston compresses the vacuum relief spring, opening the seal between the relief piston and vacuum relief seal ring and preventing a vacuum from forming in the radiator.
Other features of the disclosure will become apparent to those skilled in the art upon consideration of the following description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.